[ViewVC] Diff of: cvs/AnyEvent-MP/MP.pm

Comparing AnyEvent-MP/MP.pm (file contents):
Revision 1.50 by root, Fri Aug 14 14:01:05 2009 UTC vs.
Revision 1.76 by root, Mon Aug 31 18:45:05 2009 UTC

…		…
4		4
5	=head1 SYNOPSIS	5	=head1 SYNOPSIS
6		6
7	use AnyEvent::MP;	7	use AnyEvent::MP;
8		8
9	$NODE # contains this node's noderef	9	$NODE # contains this node's node ID
10	NODE # returns this node's noderef	10	NODE # returns this node's node ID
11	NODE $port # returns the noderef of the port
12		11
13	$SELF # receiving/own port id in rcv callbacks	12	$SELF # receiving/own port id in rcv callbacks
14		13
15	# initialise the node so it can send/receive messages	14	# initialise the node so it can send/receive messages
16	initialise_node; # -OR-	15	configure;
17	initialise_node "localhost:4040"; # -OR-
18	initialise_node "slave/", "localhost:4040"
19		16
20	# ports are message endpoints	17	# ports are message destinations
21		18
22	# sending messages	19	# sending messages
23	snd $port, type => data...;	20	snd $port, type => data...;
24	snd $port, @msg;	21	snd $port, @msg;
25	snd @msg_with_first_element_being_a_port;	22	snd @msg_with_first_element_being_a_port;
26		23
27	# creating/using ports, the simple way	24	# creating/using ports, the simple way
28	my $somple_port = port { my @msg = @_; 0 };	25	my $simple_port = port { my @msg = @_ };
29		26
30	# creating/using ports, type matching	27	# creating/using ports, tagged message matching
31	my $port = port;	28	my $port = port;
32	rcv $port, ping => sub { snd $_[0], "pong"; 0 };	29	rcv $port, ping => sub { snd $_[0], "pong" };
33	rcv $port, pong => sub { warn "pong received\n"; 0 };	30	rcv $port, pong => sub { warn "pong received\n" };
34		31
35	# create a port on another node	32	# create a port on another node
36	my $port = spawn $node, $initfunc, @initdata;	33	my $port = spawn $node, $initfunc, @initdata;
37		34
38	# monitoring	35	# monitoring
…		…
40	mon $port, $otherport # kill otherport on abnormal death	37	mon $port, $otherport # kill otherport on abnormal death
41	mon $port, $otherport, @msg # send message on death	38	mon $port, $otherport, @msg # send message on death
42		39
43	=head1 CURRENT STATUS	40	=head1 CURRENT STATUS
44		41
		42	bin/aemp - stable.
45	AnyEvent::MP - stable API, should work	43	AnyEvent::MP - stable API, should work.
46	AnyEvent::MP::Intro - outdated	44	AnyEvent::MP::Intro - epxlains most concepts.
47	AnyEvent::MP::Kernel - WIP
48	AnyEvent::MP::Transport - mostly stable	45	AnyEvent::MP::Kernel - mostly stable.
		46	AnyEvent::MP::Global - stable API, protocol not yet final.
49		47
50	stay tuned.	48	stay tuned.
51		49
52	=head1 DESCRIPTION	50	=head1 DESCRIPTION
53		51
54	This module (-family) implements a simple message passing framework.	52	This module (-family) implements a simple message passing framework.
55		53
56	Despite its simplicity, you can securely message other processes running	54	Despite its simplicity, you can securely message other processes running
57	on the same or other hosts.	55	on the same or other hosts, and you can supervise entities remotely.
58		56
59	For an introduction to this module family, see the L<AnyEvent::MP::Intro>	57	For an introduction to this module family, see the L<AnyEvent::MP::Intro>
60	manual page.	58	manual page and the examples under F<eg/>.
61
62	At the moment, this module family is severly broken and underdocumented,
63	so do not use. This was uploaded mainly to reserve the CPAN namespace -
64	stay tuned!
65		59
66	=head1 CONCEPTS	60	=head1 CONCEPTS
67		61
68	=over 4	62	=over 4
69		63
70	=item port	64	=item port
71		65
72	A port is something you can send messages to (with the C<snd> function).	66	A port is something you can send messages to (with the C<snd> function).
73		67
74	Some ports allow you to register C<rcv> handlers that can match specific	68	Ports allow you to register C<rcv> handlers that can match all or just
75	messages. All C<rcv> handlers will receive messages they match, messages	69	some messages. Messages send to ports will not be queued, regardless of
76	will not be queued.	70	anything was listening for them or not.
77		71
78	=item port id - C<noderef#portname>	72	=item port ID - C<nodeid#portname>
79		73
80	A port id is normaly the concatenation of a noderef, a hash-mark (C<#>) as	74	A port ID is the concatenation of a node ID, a hash-mark (C<#>) as
81	separator, and a port name (a printable string of unspecified format). An	75	separator, and a port name (a printable string of unspecified format).
82	exception is the the node port, whose ID is identical to its node
83	reference.
84		76
85	=item node	77	=item node
86		78
87	A node is a single process containing at least one port - the node	79	A node is a single process containing at least one port - the node port,
88	port. You can send messages to node ports to find existing ports or to	80	which enables nodes to manage each other remotely, and to create new
89	create new ports, among other things.	81	ports.
90		82
91	Nodes are either private (single-process only), slaves (connected to a	83	Nodes are either public (have one or more listening ports) or private
92	master node only) or public nodes (connectable from unrelated nodes).	84	(no listening ports). Private nodes cannot talk to other private nodes
		85	currently.
93		86
94	=item noderef - C<host:port,host:port...>, C<id@noderef>, C<id>	87	=item node ID - C<[a-za-Z0-9_\-.:]+>
95		88
96	A node reference is a string that either simply identifies the node (for	89	A node ID is a string that uniquely identifies the node within a
97	private and slave nodes), or contains a recipe on how to reach a given	90	network. Depending on the configuration used, node IDs can look like a
98	node (for public nodes).	91	hostname, a hostname and a port, or a random string. AnyEvent::MP itself
		92	doesn't interpret node IDs in any way.
99		93
100	This recipe is simply a comma-separated list of C<address:port> pairs (for	94	=item binds - C<ip:port>
101	TCP/IP, other protocols might look different).
102		95
103	Node references come in two flavours: resolved (containing only numerical	96	Nodes can only talk to each other by creating some kind of connection to
104	addresses) or unresolved (where hostnames are used instead of addresses).	97	each other. To do this, nodes should listen on one or more local transport
		98	endpoints - binds. Currently, only standard C<ip:port> specifications can
		99	be used, which specify TCP ports to listen on.
105		100
106	Before using an unresolved node reference in a message you first have to	101	=item seeds - C<host:port>
107	resolve it.	102
		103	When a node starts, it knows nothing about the network. To teach the node
		104	about the network it first has to contact some other node within the
		105	network. This node is called a seed.
		106
		107	Seeds are transport endpoint(s) of as many nodes as one wants. Those nodes
		108	are expected to be long-running, and at least one of those should always
		109	be available. When nodes run out of connections (e.g. due to a network
		110	error), they try to re-establish connections to some seednodes again to
		111	join the network.
		112
		113	Apart from being sued for seeding, seednodes are not special in any way -
		114	every public node can be a seednode.
108		115
109	=back	116	=back
110		117
111	=head1 VARIABLES/FUNCTIONS	118	=head1 VARIABLES/FUNCTIONS
112		119
…		…
127	use base "Exporter";	134	use base "Exporter";
128		135
129	our $VERSION = $AnyEvent::MP::Kernel::VERSION;	136	our $VERSION = $AnyEvent::MP::Kernel::VERSION;
130		137
131	our @EXPORT = qw(	138	our @EXPORT = qw(
132	NODE $NODE *SELF node_of _any_	139	NODE $NODE *SELF node_of after
133	resolve_node initialise_node	140	configure
134	snd rcv mon kil reg psub spawn	141	snd rcv mon mon_guard kil reg psub spawn
135	port	142	port
136	);	143	);
137		144
138	our $SELF;	145	our $SELF;
139		146
…		…
143	kil $SELF, die => $msg;	150	kil $SELF, die => $msg;
144	}	151	}
145		152
146	=item $thisnode = NODE / $NODE	153	=item $thisnode = NODE / $NODE
147		154
148	The C<NODE> function returns, and the C<$NODE> variable contains	155	The C<NODE> function returns, and the C<$NODE> variable contains, the node
149	the noderef of the local node. The value is initialised by a call	156	ID of the node running in the current process. This value is initialised by
150	to C<become_public> or C<become_slave>, after which all local port	157	a call to C<configure>.
151	identifiers become invalid.
152		158
153	=item $noderef = node_of $port	159	=item $nodeid = node_of $port
154		160
155	Extracts and returns the noderef from a portid or a noderef.	161	Extracts and returns the node ID from a port ID or a node ID.
156		162
157	=item initialise_node $noderef, $seednode, $seednode...	163	=item configure key => value...
158		164
159	=item initialise_node "slave/", $master, $master...
160
161	Before a node can talk to other nodes on the network it has to initialise	165	Before a node can talk to other nodes on the network (i.e. enter
162	itself - the minimum a node needs to know is it's own name, and optionally	166	"distributed mode") it has to configure itself - the minimum a node needs
163	it should know the noderefs of some other nodes in the network.	167	to know is its own name, and optionally it should know the addresses of
		168	some other nodes in the network to discover other nodes.
164		169
165	This function initialises a node - it must be called exactly once (or	170	This function configures a node - it must be called exactly once (or
166	never) before calling other AnyEvent::MP functions.	171	never) before calling other AnyEvent::MP functions.
167		172
168	All arguments (optionally except for the first) are noderefs, which can be
169	either resolved or unresolved.
170
171	The first argument will be looked up in the configuration database first
172	(if it is C<undef> then the current nodename will be used instead) to find
173	the relevant configuration profile (see L<aemp>). If none is found then
174	the default configuration is used. The configuration supplies additional
175	seed/master nodes and can override the actual noderef.
176
177	There are two types of networked nodes, public nodes and slave nodes:
178
179	=over 4	173	=over 4
180		174
181	=item public nodes	175	=item step 1, gathering configuration from profiles
182		176
183	For public nodes, C<$noderef> (supplied either directly to	177	The function first looks up a profile in the aemp configuration (see the
184	C<initialise_node> or indirectly via a profile or the nodename) must be a	178	L<aemp> commandline utility). The profile name can be specified via the
185	noderef (possibly unresolved, in which case it will be resolved).	179	named C<profile> parameter. If it is missing, then the nodename (F<uname
		180	-n>) will be used as profile name.
186		181
187	After resolving, the node will bind itself on all endpoints and try to	182	The profile data is then gathered as follows:
188	connect to all additional C<$seednodes> that are specified. Seednodes are
189	optional and can be used to quickly bootstrap the node into an existing
190	network.
191		183
192	=item slave nodes	184	First, all remaining key => value pairs (all of which are conviniently
		185	undocumented at the moment) will be interpreted as configuration
		186	data. Then they will be overwritten by any values specified in the global
		187	default configuration (see the F<aemp> utility), then the chain of
		188	profiles chosen by the profile name (and any C<parent> attributes).
193		189
194	When the C<$noderef> (either as given or overriden by the config file)	190	That means that the values specified in the profile have highest priority
195	is the special string C<slave/>, then the node will become a slave	191	and the values specified directly via C<configure> have lowest priority,
196	node. Slave nodes cannot be contacted from outside and will route most of	192	and can only be used to specify defaults.
197	their traffic to the master node that they attach to.
198		193
199	At least one additional noderef is required (either by specifying it	194	If the profile specifies a node ID, then this will become the node ID of
200	directly or because it is part of the configuration profile): The node	195	this process. If not, then the profile name will be used as node ID. The
201	will try to connect to all of them and will become a slave attached to the	196	special node ID of C<anon/> will be replaced by a random node ID.
202	first node it can successfully connect to.	197
		198	=item step 2, bind listener sockets
		199
		200	The next step is to look up the binds in the profile, followed by binding
		201	aemp protocol listeners on all binds specified (it is possible and valid
		202	to have no binds, meaning that the node cannot be contacted form the
		203	outside. This means the node cannot talk to other nodes that also have no
		204	binds, but it can still talk to all "normal" nodes).
		205
		206	If the profile does not specify a binds list, then a default of C<*> is
		207	used, meaning the node will bind on a dynamically-assigned port on every
		208	local IP address it finds.
		209
		210	=item step 3, connect to seed nodes
		211
		212	As the last step, the seeds list from the profile is passed to the
		213	L<AnyEvent::MP::Global> module, which will then use it to keep
		214	connectivity with at least one node at any point in time.
203		215
204	=back	216	=back
205		217
206	This function will block until all nodes have been resolved and, for slave	218	Example: become a distributed node using the locla node name as profile.
207	nodes, until it has successfully established a connection to a master	219	This should be the most common form of invocation for "daemon"-type nodes.
208	server.
209		220
210	Example: become a public node listening on the guessed noderef, or the one	221	configure
211	specified via C<aemp> for the current node. This should be the most common
212	form of invocation for "daemon"-type nodes.
213		222
214	initialise_node;	223	Example: become an anonymous node. This form is often used for commandline
		224	clients.
215		225
216	Example: become a slave node to any of the the seednodes specified via	226	configure nodeid => "anon/";
217	C<aemp>. This form is often used for commandline clients.
218		227
219	initialise_node "slave/";	228	Example: configure a node using a profile called seed, which si suitable
		229	for a seed node as it binds on all local addresses on a fixed port (4040,
		230	customary for aemp).
220		231
221	Example: become a slave node to any of the specified master servers. This	232	# use the aemp commandline utility
222	form is also often used for commandline clients.	233	# aemp profile seed nodeid anon/ binds '*:4040'
223		234
224	initialise_node "slave/", "master1", "192.168.13.17", "mp.example.net";	235	# then use it
		236	configure profile => "seed";
225		237
226	Example: become a public node, and try to contact some well-known master	238	# or simply use aemp from the shell again:
227	servers to become part of the network.	239	# aemp run profile seed
228		240
229	initialise_node undef, "master1", "master2";	241	# or provide a nicer-to-remember nodeid
230		242	# aemp run profile seed nodeid "$(hostname)"
231	Example: become a public node listening on port C<4041>.
232
233	initialise_node 4041;
234
235	Example: become a public node, only visible on localhost port 4044.
236
237	initialise_node "localhost:4044";
238
239	=item $cv = resolve_node $noderef
240
241	Takes an unresolved node reference that may contain hostnames and
242	abbreviated IDs, resolves all of them and returns a resolved node
243	reference.
244
245	In addition to C<address:port> pairs allowed in resolved noderefs, the
246	following forms are supported:
247
248	=over 4
249
250	=item the empty string
251
252	An empty-string component gets resolved as if the default port (4040) was
253	specified.
254
255	=item naked port numbers (e.g. C<1234>)
256
257	These are resolved by prepending the local nodename and a colon, to be
258	further resolved.
259
260	=item hostnames (e.g. C<localhost:1234>, C<localhost>)
261
262	These are resolved by using AnyEvent::DNS to resolve them, optionally
263	looking up SRV records for the C<aemp=4040> port, if no port was
264	specified.
265
266	=back
267		243
268	=item $SELF	244	=item $SELF
269		245
270	Contains the current port id while executing C<rcv> callbacks or C<psub>	246	Contains the current port id while executing C<rcv> callbacks or C<psub>
271	blocks.	247	blocks.
272		248
273	=item SELF, %SELF, @SELF...	249	=item *SELF, SELF, %SELF, @SELF...
274		250
275	Due to some quirks in how perl exports variables, it is impossible to	251	Due to some quirks in how perl exports variables, it is impossible to
276	just export C<$SELF>, all the symbols called C<SELF> are exported by this	252	just export C<$SELF>, all the symbols named C<SELF> are exported by this
277	module, but only C<$SELF> is currently used.	253	module, but only C<$SELF> is currently used.
278		254
279	=item snd $port, type => @data	255	=item snd $port, type => @data
280		256
281	=item snd $port, @msg	257	=item snd $port, @msg
282		258
283	Send the given message to the given port ID, which can identify either	259	Send the given message to the given port, which can identify either a
284	a local or a remote port, and can be either a string or soemthignt hat	260	local or a remote port, and must be a port ID.
285	stringifies a sa port ID (such as a port object :).
286		261
287	While the message can be about anything, it is highly recommended to use a	262	While the message can be almost anything, it is highly recommended to
288	string as first element (a portid, or some word that indicates a request	263	use a string as first element (a port ID, or some word that indicates a
289	type etc.).	264	request type etc.) and to consist if only simple perl values (scalars,
		265	arrays, hashes) - if you think you need to pass an object, think again.
290		266
291	The message data effectively becomes read-only after a call to this	267	The message data logically becomes read-only after a call to this
292	function: modifying any argument is not allowed and can cause many	268	function: modifying any argument (or values referenced by them) is
293	problems.	269	forbidden, as there can be considerable time between the call to C<snd>
		270	and the time the message is actually being serialised - in fact, it might
		271	never be copied as within the same process it is simply handed to the
		272	receiving port.
294		273
295	The type of data you can transfer depends on the transport protocol: when	274	The type of data you can transfer depends on the transport protocol: when
296	JSON is used, then only strings, numbers and arrays and hashes consisting	275	JSON is used, then only strings, numbers and arrays and hashes consisting
297	of those are allowed (no objects). When Storable is used, then anything	276	of those are allowed (no objects). When Storable is used, then anything
298	that Storable can serialise and deserialise is allowed, and for the local	277	that Storable can serialise and deserialise is allowed, and for the local
299	node, anything can be passed.	278	node, anything can be passed. Best rely only on the common denominator of
		279	these.
300		280
301	=item $local_port = port	281	=item $local_port = port
302		282
303	Create a new local port object and returns its port ID. Initially it has	283	Create a new local port object and returns its port ID. Initially it has
304	no callbacks set and will throw an error when it receives messages.	284	no callbacks set and will throw an error when it receives messages.
…		…
351	The default callback received all messages not matched by a more specific	331	The default callback received all messages not matched by a more specific
352	C<tag> match.	332	C<tag> match.
353		333
354	=item rcv $local_port, tag => $callback->(@msg_without_tag), ...	334	=item rcv $local_port, tag => $callback->(@msg_without_tag), ...
355		335
356	Register callbacks to be called on messages starting with the given tag on	336	Register (or replace) callbacks to be called on messages starting with the
357	the given port (and return the port), or unregister it (when C<$callback>	337	given tag on the given port (and return the port), or unregister it (when
358	is C<$undef>).	338	C<$callback> is C<$undef> or missing). There can only be one callback
		339	registered for each tag.
359		340
360	The original message will be passed to the callback, after the first	341	The original message will be passed to the callback, after the first
361	element (the tag) has been removed. The callback will use the same	342	element (the tag) has been removed. The callback will use the same
362	environment as the default callback (see above).	343	environment as the default callback (see above).
363		344
…		…
375	rcv port,	356	rcv port,
376	msg1 => sub { ... },	357	msg1 => sub { ... },
377	...	358	...
378	;	359	;
379		360
		361	Example: temporarily register a rcv callback for a tag matching some port
		362	(e.g. for a rpc reply) and unregister it after a message was received.
		363
		364	rcv $port, $otherport => sub {
		365	my @reply = @_;
		366
		367	rcv $SELF, $otherport;
		368	};
		369
380	=cut	370	=cut
381		371
382	sub rcv($@) {	372	sub rcv($@) {
383	my $port = shift;	373	my $port = shift;
384	my ($noderef, $portid) = split /#/, $port, 2;	374	my ($nodeid, $portid) = split /#/, $port, 2;
385		375
386	($NODE{$noderef} \|\| add_node $noderef) == $NODE{""}	376	$NODE{$nodeid} == $NODE{""}
387	or Carp::croak "$port: rcv can only be called on local ports, caught";	377	or Carp::croak "$port: rcv can only be called on local ports, caught";
388		378
389	while (@_) {	379	while (@_) {
390	if (ref $_[0]) {	380	if (ref $_[0]) {
391	if (my $self = $PORT_DATA{$portid}) {	381	if (my $self = $PORT_DATA{$portid}) {
…		…
470	$res	460	$res
471	}	461	}
472	}	462	}
473	}	463	}
474		464
475	=item $guard = mon $port, $cb->(@reason)	465	=item $guard = mon $port, $cb->(@reason) # call $cb when $port dies
476		466
477	=item $guard = mon $port, $rcvport	467	=item $guard = mon $port, $rcvport # kill $rcvport when $port dies
478		468
479	=item $guard = mon $port	469	=item $guard = mon $port # kill $SELF when $port dies
480		470
481	=item $guard = mon $port, $rcvport, @msg	471	=item $guard = mon $port, $rcvport, @msg # send a message when $port dies
482		472
483	Monitor the given port and do something when the port is killed or	473	Monitor the given port and do something when the port is killed or
484	messages to it were lost, and optionally return a guard that can be used	474	messages to it were lost, and optionally return a guard that can be used
485	to stop monitoring again.	475	to stop monitoring again.
486		476
487	C<mon> effectively guarantees that, in the absence of hardware failures,	477	C<mon> effectively guarantees that, in the absence of hardware failures,
488	that after starting the monitor, either all messages sent to the port	478	after starting the monitor, either all messages sent to the port will
489	will arrive, or the monitoring action will be invoked after possible	479	arrive, or the monitoring action will be invoked after possible message
490	message loss has been detected. No messages will be lost "in between"	480	loss has been detected. No messages will be lost "in between" (after
491	(after the first lost message no further messages will be received by the	481	the first lost message no further messages will be received by the
492	port). After the monitoring action was invoked, further messages might get	482	port). After the monitoring action was invoked, further messages might get
493	delivered again.	483	delivered again.
		484
		485	Note that monitoring-actions are one-shot: once messages are lost (and a
		486	monitoring alert was raised), they are removed and will not trigger again.
494		487
495	In the first form (callback), the callback is simply called with any	488	In the first form (callback), the callback is simply called with any
496	number of C<@reason> elements (no @reason means that the port was deleted	489	number of C<@reason> elements (no @reason means that the port was deleted
497	"normally"). Note also that I<< the callback B<must> never die >>, so use	490	"normally"). Note also that I<< the callback B<must> never die >>, so use
498	C<eval> if unsure.	491	C<eval> if unsure.
…		…
528	mon $port, $self => "restart";	521	mon $port, $self => "restart";
529		522
530	=cut	523	=cut
531		524
532	sub mon {	525	sub mon {
533	my ($noderef, $port) = split /#/, shift, 2;	526	my ($nodeid, $port) = split /#/, shift, 2;
534		527
535	my $node = $NODE{$noderef} \|\| add_node $noderef;	528	my $node = $NODE{$nodeid} \|\| add_node $nodeid;
536		529
537	my $cb = @_ ? shift : $SELF \|\| Carp::croak 'mon: called with one argument only, but $SELF not set,';	530	my $cb = @_ ? shift : $SELF \|\| Carp::croak 'mon: called with one argument only, but $SELF not set,';
538		531
539	unless (ref $cb) {	532	unless (ref $cb) {
540	if (@_) {	533	if (@_) {
…		…
560	is killed, the references will be freed.	553	is killed, the references will be freed.
561		554
562	Optionally returns a guard that will stop the monitoring.	555	Optionally returns a guard that will stop the monitoring.
563		556
564	This function is useful when you create e.g. timers or other watchers and	557	This function is useful when you create e.g. timers or other watchers and
565	want to free them when the port gets killed:	558	want to free them when the port gets killed (note the use of C<psub>):
566		559
567	$port->rcv (start => sub {	560	$port->rcv (start => sub {
568	my $timer; $timer = mon_guard $port, AE::timer 1, 1, sub {	561	my $timer; $timer = mon_guard $port, AE::timer 1, 1, psub {
569	undef $timer if 0.9 < rand;	562	undef $timer if 0.9 < rand;
570	});	563	});
571	});	564	});
572		565
573	=cut	566	=cut
…		…
582		575
583	=item kil $port[, @reason]	576	=item kil $port[, @reason]
584		577
585	Kill the specified port with the given C<@reason>.	578	Kill the specified port with the given C<@reason>.
586		579
587	If no C<@reason> is specified, then the port is killed "normally" (linked	580	If no C<@reason> is specified, then the port is killed "normally" (ports
588	ports will not be kileld, or even notified).	581	monitoring other ports will not necessarily die because a port dies
		582	"normally").
589		583
590	Otherwise, linked ports get killed with the same reason (second form of	584	Otherwise, linked ports get killed with the same reason (second form of
591	C<mon>, see below).	585	C<mon>, see above).
592		586
593	Runtime errors while evaluating C<rcv> callbacks or inside C<psub> blocks	587	Runtime errors while evaluating C<rcv> callbacks or inside C<psub> blocks
594	will be reported as reason C<< die => $@ >>.	588	will be reported as reason C<< die => $@ >>.
595		589
596	Transport/communication errors are reported as C<< transport_error =>	590	Transport/communication errors are reported as C<< transport_error =>
…		…
601	=item $port = spawn $node, $initfunc[, @initdata]	595	=item $port = spawn $node, $initfunc[, @initdata]
602		596
603	Creates a port on the node C<$node> (which can also be a port ID, in which	597	Creates a port on the node C<$node> (which can also be a port ID, in which
604	case it's the node where that port resides).	598	case it's the node where that port resides).
605		599
606	The port ID of the newly created port is return immediately, and it is	600	The port ID of the newly created port is returned immediately, and it is
607	permissible to immediately start sending messages or monitor the port.	601	possible to immediately start sending messages or to monitor the port.
608		602
609	After the port has been created, the init function is	603	After the port has been created, the init function is called on the remote
610	called. This function must be a fully-qualified function name	604	node, in the same context as a C<rcv> callback. This function must be a
611	(e.g. C<MyApp::Chat::Server::init>). To specify a function in the main	605	fully-qualified function name (e.g. C<MyApp::Chat::Server::init>). To
612	program, use C<::name>.	606	specify a function in the main program, use C<::name>.
613		607
614	If the function doesn't exist, then the node tries to C<require>	608	If the function doesn't exist, then the node tries to C<require>
615	the package, then the package above the package and so on (e.g.	609	the package, then the package above the package and so on (e.g.
616	C<MyApp::Chat::Server>, C<MyApp::Chat>, C<MyApp>) until the function	610	C<MyApp::Chat::Server>, C<MyApp::Chat>, C<MyApp>) until the function
617	exists or it runs out of package names.	611	exists or it runs out of package names.
618		612
619	The init function is then called with the newly-created port as context	613	The init function is then called with the newly-created port as context
620	object (C<$SELF>) and the C<@initdata> values as arguments.	614	object (C<$SELF>) and the C<@initdata> values as arguments.
621		615
622	A common idiom is to pass your own port, monitor the spawned port, and	616	A common idiom is to pass a local port, immediately monitor the spawned
623	in the init function, monitor the original port. This two-way monitoring	617	port, and in the remote init function, immediately monitor the passed
624	ensures that both ports get cleaned up when there is a problem.	618	local port. This two-way monitoring ensures that both ports get cleaned up
		619	when there is a problem.
625		620
626	Example: spawn a chat server port on C<$othernode>.	621	Example: spawn a chat server port on C<$othernode>.
627		622
628	# this node, executed from within a port context:	623	# this node, executed from within a port context:
629	my $server = spawn $othernode, "MyApp::Chat::Server::connect", $SELF;	624	my $server = spawn $othernode, "MyApp::Chat::Server::connect", $SELF;
…		…
652	};	647	};
653	_self_die if $@;	648	_self_die if $@;
654	}	649	}
655		650
656	sub spawn(@) {	651	sub spawn(@) {
657	my ($noderef, undef) = split /#/, shift, 2;	652	my ($nodeid, undef) = split /#/, shift, 2;
658		653
659	my $id = "$RUNIQ." . $ID++;	654	my $id = "$RUNIQ." . $ID++;
660		655
661	$_[0] =~ /::/	656	$_[0] =~ /::/
662	or Carp::croak "spawn init function must be a fully-qualified name, caught";	657	or Carp::croak "spawn init function must be a fully-qualified name, caught";
663		658
664	($NODE{$noderef} \|\| add_node $noderef)	659	snd_to_func $nodeid, "AnyEvent::MP::_spawn" => $id, @_;
665	->send (["", "AnyEvent::MP::_spawn" => $id, @_]);
666		660
667	"$noderef#$id"	661	"$nodeid#$id"
668	}	662	}
669		663
670	=back	664	=item after $timeout, @msg
671		665
672	=head1 NODE MESSAGES	666	=item after $timeout, $callback
673		667
674	Nodes understand the following messages sent to them. Many of them take	668	Either sends the given message, or call the given callback, after the
675	arguments called C<@reply>, which will simply be used to compose a reply	669	specified number of seconds.
676	message - C<$reply[0]> is the port to reply to, C<$reply[1]> the type and
677	the remaining arguments are simply the message data.
678		670
679	While other messages exist, they are not public and subject to change.	671	This is simply a utility function that comes in handy at times - the
		672	AnyEvent::MP author is not convinced of the wisdom of having it, though,
		673	so it may go away in the future.
680		674
681	=over 4
682
683	=cut	675	=cut
684		676
685	=item lookup => $name, @reply	677	sub after($@) {
		678	my ($timeout, @action) = @_;
686		679
687	Replies with the port ID of the specified well-known port, or C<undef>.	680	my $t; $t = AE::timer $timeout, 0, sub {
688		681	undef $t;
689	=item devnull => ...	682	ref $action[0]
690		683	? $action[0]()
691	Generic data sink/CPU heat conversion.	684	: snd @action;
692		685	};
693	=item relay => $port, @msg	686	}
694
695	Simply forwards the message to the given port.
696
697	=item eval => $string[ @reply]
698
699	Evaluates the given string. If C<@reply> is given, then a message of the
700	form C<@reply, $@, @evalres> is sent.
701
702	Example: crash another node.
703
704	snd $othernode, eval => "exit";
705
706	=item time => @reply
707
708	Replies the the current node time to C<@reply>.
709
710	Example: tell the current node to send the current time to C<$myport> in a
711	C<timereply> message.
712
713	snd $NODE, time => $myport, timereply => 1, 2;
714	# => snd $myport, timereply => 1, 2, <time>
715		687
716	=back	688	=back
717		689
718	=head1 AnyEvent::MP vs. Distributed Erlang	690	=head1 AnyEvent::MP vs. Distributed Erlang
719		691
…		…
729		701
730	Despite the similarities, there are also some important differences:	702	Despite the similarities, there are also some important differences:
731		703
732	=over 4	704	=over 4
733		705
734	=item * Node references contain the recipe on how to contact them.	706	=item * Node IDs are arbitrary strings in AEMP.
735		707
736	Erlang relies on special naming and DNS to work everywhere in the	708	Erlang relies on special naming and DNS to work everywhere in the same
737	same way. AEMP relies on each node knowing it's own address(es), with	709	way. AEMP relies on each node somehow knowing its own address(es) (e.g. by
738	convenience functionality.	710	configuraiton or DNS), but will otherwise discover other odes itself.
739		711
740	This means that AEMP requires a less tightly controlled environment at the	712	=item * Erlang has a "remote ports are like local ports" philosophy, AEMP
741	cost of longer node references and a slightly higher management overhead.	713	uses "local ports are like remote ports".
		714
		715	The failure modes for local ports are quite different (runtime errors
		716	only) then for remote ports - when a local port dies, you I<know> it dies,
		717	when a connection to another node dies, you know nothing about the other
		718	port.
		719
		720	Erlang pretends remote ports are as reliable as local ports, even when
		721	they are not.
		722
		723	AEMP encourages a "treat remote ports differently" philosophy, with local
		724	ports being the special case/exception, where transport errors cannot
		725	occur.
742		726
743	=item * Erlang uses processes and a mailbox, AEMP does not queue.	727	=item * Erlang uses processes and a mailbox, AEMP does not queue.
744		728
745	Erlang uses processes that selctively receive messages, and therefore	729	Erlang uses processes that selectively receive messages, and therefore
746	needs a queue. AEMP is event based, queuing messages would serve no useful	730	needs a queue. AEMP is event based, queuing messages would serve no
747	purpose.	731	useful purpose. For the same reason the pattern-matching abilities of
		732	AnyEvent::MP are more limited, as there is little need to be able to
		733	filter messages without dequeing them.
748		734
749	(But see L<Coro::MP> for a more Erlang-like process model on top of AEMP).	735	(But see L<Coro::MP> for a more Erlang-like process model on top of AEMP).
750		736
751	=item * Erlang sends are synchronous, AEMP sends are asynchronous.	737	=item * Erlang sends are synchronous, AEMP sends are asynchronous.
752		738
753	Sending messages in Erlang is synchronous and blocks the process. AEMP	739	Sending messages in Erlang is synchronous and blocks the process (and
754	sends are immediate, connection establishment is handled in the	740	so does not need a queue that can overflow). AEMP sends are immediate,
755	background.	741	connection establishment is handled in the background.
756		742
757	=item * Erlang can silently lose messages, AEMP cannot.	743	=item * Erlang suffers from silent message loss, AEMP does not.
758		744
759	Erlang makes few guarantees on messages delivery - messages can get lost	745	Erlang makes few guarantees on messages delivery - messages can get lost
760	without any of the processes realising it (i.e. you send messages a, b,	746	without any of the processes realising it (i.e. you send messages a, b,
761	and c, and the other side only receives messages a and c).	747	and c, and the other side only receives messages a and c).
762		748
763	AEMP guarantees correct ordering, and the guarantee that there are no	749	AEMP guarantees correct ordering, and the guarantee that after one message
764	holes in the message sequence.	750	is lost, all following ones sent to the same port are lost as well, until
765		751	monitoring raises an error, so there are no silent "holes" in the message
766	=item * In Erlang, processes can be declared dead and later be found to be	752	sequence.
767	alive.
768
769	In Erlang it can happen that a monitored process is declared dead and
770	linked processes get killed, but later it turns out that the process is
771	still alive - and can receive messages.
772
773	In AEMP, when port monitoring detects a port as dead, then that port will
774	eventually be killed - it cannot happen that a node detects a port as dead
775	and then later sends messages to it, finding it is still alive.
776		753
777	=item * Erlang can send messages to the wrong port, AEMP does not.	754	=item * Erlang can send messages to the wrong port, AEMP does not.
778		755
779	In Erlang it is quite possible that a node that restarts reuses a process	756	In Erlang it is quite likely that a node that restarts reuses a process ID
780	ID known to other nodes for a completely different process, causing	757	known to other nodes for a completely different process, causing messages
781	messages destined for that process to end up in an unrelated process.	758	destined for that process to end up in an unrelated process.
782		759
783	AEMP never reuses port IDs, so old messages or old port IDs floating	760	AEMP never reuses port IDs, so old messages or old port IDs floating
784	around in the network will not be sent to an unrelated port.	761	around in the network will not be sent to an unrelated port.
785		762
786	=item * Erlang uses unprotected connections, AEMP uses secure	763	=item * Erlang uses unprotected connections, AEMP uses secure
787	authentication and can use TLS.	764	authentication and can use TLS.
788		765
789	AEMP can use a proven protocol - SSL/TLS - to protect connections and	766	AEMP can use a proven protocol - TLS - to protect connections and
790	securely authenticate nodes.	767	securely authenticate nodes.
791		768
792	=item * The AEMP protocol is optimised for both text-based and binary	769	=item * The AEMP protocol is optimised for both text-based and binary
793	communications.	770	communications.
794		771
795	The AEMP protocol, unlike the Erlang protocol, supports both	772	The AEMP protocol, unlike the Erlang protocol, supports both programming
796	language-independent text-only protocols (good for debugging) and binary,	773	language independent text-only protocols (good for debugging) and binary,
797	language-specific serialisers (e.g. Storable).	774	language-specific serialisers (e.g. Storable). By default, unless TLS is
		775	used, the protocol is actually completely text-based.
798		776
799	It has also been carefully designed to be implementable in other languages	777	It has also been carefully designed to be implementable in other languages
800	with a minimum of work while gracefully degrading fucntionality to make the	778	with a minimum of work while gracefully degrading functionality to make the
801	protocol simple.	779	protocol simple.
802		780
803	=item * AEMP has more flexible monitoring options than Erlang.	781	=item * AEMP has more flexible monitoring options than Erlang.
804		782
805	In Erlang, you can chose to receive I<all> exit signals as messages	783	In Erlang, you can chose to receive I<all> exit signals as messages
…		…
808	Erlang, as one can choose between automatic kill, exit message or callback	786	Erlang, as one can choose between automatic kill, exit message or callback
809	on a per-process basis.	787	on a per-process basis.
810		788
811	=item * Erlang tries to hide remote/local connections, AEMP does not.	789	=item * Erlang tries to hide remote/local connections, AEMP does not.
812		790
813	Monitoring in Erlang is not an indicator of process death/crashes,	791	Monitoring in Erlang is not an indicator of process death/crashes, in the
814	as linking is (except linking is unreliable in Erlang).	792	same way as linking is (except linking is unreliable in Erlang).
815		793
816	In AEMP, you don't "look up" registered port names or send to named ports	794	In AEMP, you don't "look up" registered port names or send to named ports
817	that might or might not be persistent. Instead, you normally spawn a port	795	that might or might not be persistent. Instead, you normally spawn a port
818	on the remote node. The init function monitors the you, and you monitor	796	on the remote node. The init function monitors you, and you monitor the
819	the remote port. Since both monitors are local to the node, they are much	797	remote port. Since both monitors are local to the node, they are much more
820	more reliable.	798	reliable (no need for C<spawn_link>).
821		799
822	This also saves round-trips and avoids sending messages to the wrong port	800	This also saves round-trips and avoids sending messages to the wrong port
823	(hard to do in Erlang).	801	(hard to do in Erlang).
824		802
825	=back	803	=back
826		804
827	=head1 RATIONALE	805	=head1 RATIONALE
828		806
829	=over 4	807	=over 4
830		808
831	=item Why strings for ports and noderefs, why not objects?	809	=item Why strings for port and node IDs, why not objects?
832		810
833	We considered "objects", but found that the actual number of methods	811	We considered "objects", but found that the actual number of methods
834	thatc an be called are very low. Since port IDs and noderefs travel over	812	that can be called are quite low. Since port and node IDs travel over
835	the network frequently, the serialising/deserialising would add lots of	813	the network frequently, the serialising/deserialising would add lots of
836	overhead, as well as having to keep a proxy object.	814	overhead, as well as having to keep a proxy object everywhere.
837		815
838	Strings can easily be printed, easily serialised etc. and need no special	816	Strings can easily be printed, easily serialised etc. and need no special
839	procedures to be "valid".	817	procedures to be "valid".
840		818
841	And a a miniport consists of a single closure stored in a global hash - it	819	And as a result, a miniport consists of a single closure stored in a
842	can't become much cheaper.	820	global hash - it can't become much cheaper.
843		821
844	=item Why favour JSON, why not real serialising format such as Storable?	822	=item Why favour JSON, why not a real serialising format such as Storable?
845		823
846	In fact, any AnyEvent::MP node will happily accept Storable as framing	824	In fact, any AnyEvent::MP node will happily accept Storable as framing
847	format, but currently there is no way to make a node use Storable by	825	format, but currently there is no way to make a node use Storable by
848	default.	826	default (although all nodes will accept it).
849		827
850	The default framing protocol is JSON because a) JSON::XS is many times	828	The default framing protocol is JSON because a) JSON::XS is many times
851	faster for small messages and b) most importantly, after years of	829	faster for small messages and b) most importantly, after years of
852	experience we found that object serialisation is causing more problems	830	experience we found that object serialisation is causing more problems
853	than it gains: Just like function calls, objects simply do not travel	831	than it solves: Just like function calls, objects simply do not travel
854	easily over the network, mostly because they will always be a copy, so you	832	easily over the network, mostly because they will always be a copy, so you
855	always have to re-think your design.	833	always have to re-think your design.
856		834
857	Keeping your messages simple, concentrating on data structures rather than	835	Keeping your messages simple, concentrating on data structures rather than
858	objects, will keep your messages clean, tidy and efficient.	836	objects, will keep your messages clean, tidy and efficient.
859		837
860	=back	838	=back
861		839
862	=head1 SEE ALSO	840	=head1 SEE ALSO
863		841
		842	L<AnyEvent::MP::Intro> - a gentle introduction.
		843
		844	L<AnyEvent::MP::Kernel> - more, lower-level, stuff.
		845
		846	L<AnyEvent::MP::Global> - network maintainance and port groups, to find
		847	your applications.
		848
864	L<AnyEvent>.	849	L<AnyEvent>.
865		850
866	=head1 AUTHOR	851	=head1 AUTHOR
867		852
868	Marc Lehmann <schmorp@schmorp.de>	853	Marc Lehmann <schmorp@schmorp.de>

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Revision 1.50 by root, Fri Aug 14 14:01:05 2009 UTC vs.
Revision 1.76 by root, Mon Aug 31 18:45:05 2009 UTC